Severe Acute Respiratory Syndrome: Radiographic Features of 36 Probable Cases

The purpose of this study is to evaluate the radiographic manifestations and sequential changes of severe acute respiratory syndrome (SARS). The chest radiographs obtained in 36 patients with probable SARS were retrospectively reviewed. Radiographic features, including the patterns, distribution, and extent of involvement, were documented and sequential radiographic changes were evaluated through comparisons of the evolving density, extent, and number of lesions. Initial chest radiographs were abnormal in 30 of 36 (83%) patients and showed air-space opacity. Unifocal (13 of 30, 44%) or bilateral multifocal involvement (15 of 30, 50%) was more commonly observed. Of the total 49 lesions in 30 patients, it appeared more frequently in the lower lung zone (28 of 49, 58%), as well as in the mixed central and peripheral regions (26 of 49, 53%). There was no evidence of cavitation, adenopathy, or pleural effusion on any of the initial chest radiographs. Except for two patients without significant abnormality, four patterns of sequential radiographic changes were recognized: type1 (progressive improvement) in 4 of 34 patients (12%), type 2 (initial worsening followed by progressive improvement) in 14 patients (41%), type 3 (fluctuating changes) in 13 patients (38%), and type 4 (progressive worsening) in 3 patients (9%). Although SARS had a variety of radiographic appearances, typical findings were predominantly unifocal or multifocal air-space opacity, lower lobe predominance, and lack of cavitation, adenopathy, and pleural effusion.